Systems and methods for determining duct leakage in a climate control system

ABSTRACT

Methods and related systems for operating a climate control system for an indoor space are disclosed. In an embodiment, the method includes operating an indoor fan of the climate control system to rotate an impeller of the indoor fan in a reverse rotational direction opposite a nominal rotational direction of the impeller. Additionally, the method includes determining an airflow of the indoor fan when the impeller of the indoor fan is rotated in the reverse rotational direction. Further, the method includes determining a duct leakage rate associated with at least one duct of the climate control system based on the determined airflow, wherein the at least one duct is sealed-off at an end thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND

Climate control systems, such as heating, ventilation, and/or airconditioning (HVAC) systems may generally be used in residential and/orcommercial areas for heating and/or cooling an indoor space to createcomfortable temperatures inside those areas. Some climate controlsystems may be split-type air conditioning or heat pump systems. Thesesystems typically have an indoor unit and an outdoor unit which arecapable of cooling a comfort zone by operating in a cooling mode fortransferring heat from a comfort zone to an ambient zone using arefrigeration cycle. Heat pump systems are also generally capable ofreversing the direction of refrigerant flow through the components ofthe climate control system so that heat is transferred from the ambientzone to the comfort zone, thereby heating the comfort zone.

In some applications, the indoor unit of a climate control system for anindoor space may include an indoor fan for providing airflow through theindoor unit along an air circulation path of the climate control system.In some applications, the air circulation path of the climate controlsystem may be defined by one more supply ducts and one or more returnducts extending between the indoor unit and the indoor space. If aportion of the airflow in the at least one duct of the climate controlsystem leaks from said duct prior to being supplied to the indoor spaceand/or being returned to the indoor unit, the performance of the climatecontrol system is reduced.

BRIEF SUMMARY

Some embodiments disclosed herein are directed to a method of operatinga climate control system for an indoor space. In an embodiment, themethod includes operating an indoor fan of the climate control system torotate an impeller of the indoor fan in a reverse rotational directionopposite a nominal rotational direction of the impeller. Additionally,the method includes determining an airflow of the indoor fan when theimpeller of the indoor fan is rotated in the reverse rotationaldirection. Further, the method includes determining a duct leakage rateassociated with at least one duct of the climate control system based onthe determined airflow, wherein airflow through the at least one duct isrestricted.

Other embodiments disclosed herein are directed to a climate controlsystem for an indoor space. In an embodiment, the climate control systemincludes an indoor fan configured to produce an airflow through theindoor space, and at least one duct defining an air circulation path ofthe indoor space, wherein airflow through the at least one duct isrestricted. In addition, the climate control system includes acontroller to be coupled to the indoor fan. The controller is configuredto operate the indoor fan to rotate an impeller of the indoor fan in areverse rotational direction opposite a nominal rotational direction ofthe impeller. In addition, the controller is configured to determine anairflow of the indoor fan when the impeller of the indoor fan is rotatedin the reverse rotational direction. Further, the controller isconfigured to determine a duct leakage rate associated with the at leastone duct based on the airflow of the indoor fan.

Embodiments described herein comprise a combination of features andcharacteristics intended to address various shortcomings associated withcertain prior devices, systems, and methods. The foregoing has outlinedrather broadly the features and technical characteristics of thedisclosed embodiments in order that the detailed description thatfollows may be better understood. The various characteristics andfeatures described above, as well as others, will be readily apparent tothose skilled in the art upon reading the following detaileddescription, and by referring to the accompanying drawings. It should beappreciated that the conception and the specific embodiments disclosedmay be readily utilized as a basis for modifying or designing otherstructures for carrying out the same purposes as the disclosedembodiments. It should also be realized that such equivalentconstructions do not depart from the spirit and scope of the principlesdisclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of various exemplary embodiments, referencewill now be made to the accompanying drawings in which:

FIG. 1 is a diagram of a HVAC system configured for operating in acooling mode according to some embodiments;

FIG. 2 is a schematic diagram of an air circulation path of the HVACsystem of FIG. 1 according to an embodiment of the disclosure; and

FIG. 3 is a flow chart of a method of determining duct leakage in aclimate control system according to some embodiments.

DETAILED DESCRIPTION

The following discussion is directed to various exemplary embodiments.However, one of ordinary skill in the art will understand that theexamples disclosed herein have broad application, and that thediscussion of any embodiment is meant only to be exemplary of thatembodiment, and not intended to suggest that the scope of thedisclosure, including the claims, is limited to that embodiment.

The drawing figures are not necessarily to scale. Certain features andcomponents herein may be shown exaggerated in scale or in somewhatschematic form and some details of conventional elements may not beshown in interest of clarity and conciseness.

In the following discussion and in the claims, the terms “including” and“comprising” are used in an open-ended fashion, and thus should beinterpreted to mean “including, but not limited to . . . .” Also, theterm “couple” or “couples” is intended to mean either an indirect ordirect connection. Thus, if a first device couples to a second device,that connection may be through a direct connection of the two devices,or through an indirect connection that is established via other devices,components, nodes, and connections. In addition, as used herein, theterms “axial” and “axially” generally mean along or parallel to a givenaxis (e.g., central axis of a body or a port), while the terms “radial”and “radially” generally mean perpendicular to the given axis. Forinstance, an axial distance refers to a distance measured along orparallel to the axis, and a radial distance means a distance measuredperpendicular to the axis. Further, when used herein (including in theclaims), the words “about,” “generally,” “substantially,”“approximately,” and the like mean within a range of plus or minus 10%.

As described above, an indoor unit of a climate control system for anindoor space may include an indoor fan for providing airflow through anindoor unit of the climate control system. Additionally, the indoor fanmay provide airflow along an air circulation path defined by at leastone duct of the climate control system that extends between the indoorunit and the indoor space. If not properly installed or maintained,airflow in the at least one duct of the climate control system may leakfrom the at least one duct prior to being supplied to the indoor spaceand/or being returned to the indoor unit. For instance, airflow in asupply duct of the climate control system may leak from the supply ductbefore being supplied to the indoor space, and/or at least some of theairflow in a return duct of the climate control system may leak from thereturn duct before being returned to the indoor unit.

The amount or rate of leakage in the duct(s) of the climate controlsystem may be evaluated or monitored to determine if the leakage rate isabove a predetermined maximum permissible leakage rate. For instance,the maximum permissible leakage rate may be a leakage rate greater thana leakage rate to be expected in a newly and properly installed climatecontrol system in typical applications. In some conventional climatecontrol systems for indoor spaces, specialized equipment is utilized todetermine the amount of airflow leakage in the duct(s) of the climatecontrol system. For instance, a specialized fan provided by a thirdparty and having an airflow sensor may be attached to a registerdefining an interface between one of the ducts and the indoor spacewhile the remaining ducts of the climate control system are sealed bythe third party so that the fan may pressurize the ducts of the climatecontrol system and determine the amount of airflow that may be producedin the sealed ducts, where the amount of produced airflow corresponds tothe amount of leakage in the sealed ducts.

However, the utilization of specialized equipment provided by thirdparties for determining duct leakage may increase the cost, complexity,and time required for determining duct leakage in the climate controlsystem. Additionally, utilizing a fan located externally of the indoorunit (e.g., a fan attached to a register positioned at an end of one ofthe duct(s) of the climate control system) may allow only for thedetermination of leakage in all of the ducts of the climate controlsystem. In other words, utilizing an external fan may not allow for thesupply ducts and return ducts of the climate control system to beevaluated independently of each other to determine if the leak (ifpresent) stems from either the supply or return ducts.

For example, if the external fan is attached to a supply duct, then,upon activation, the external fan will produce a positive airflow intoand through both the supply duct and return duct (the return duct beingpositioned downstream from the supply duct relative to the external fanin this arrangement) given that the indoor fan (being positioned betweenthe supply and return ducts) of the climate control system is typicallyincapable of sealing the supply duct from the return duct (andvice-a-versa). Given that the airflow produced by the external fan flowsboth into and through the supply duct and return duct, any leak formedin either the supply duct or return duct will contribute to the leakagerate determined by the external fan.

Accordingly, embodiments disclosed herein include systems and methodsfor determining duct leakage in a climate control system that utilizesthe indoor fan of the climate control system and thus does not rely onspecialized equipment provided by a third party. Particularly,embodiments disclosed herein include systems and methods for determiningduct leakage in the climate control system that includes operating anindoor fan of the climate control system to rotate an impeller of theindoor fan in a reverse rotational direction opposite a nominalrotational direction of the impeller whereby a fan efficiency of theindoor fan is reduced, determining an airflow of the indoor fan when theimpeller of the indoor fan is rotated in the reverse rotationaldirection, and determining a duct leakage rate associated with the atleast one duct based on the airflow of the indoor fan, wherein airflowthrough the at least one duct is restricted.

As will be described in more detail below, use of the embodimentsdisclosed herein may allow duct leakage to be continually monitored overthe operational life of the climate control system such that any issuesor problems related to excessive duct leakage that may interfere withthe performance of the climate control system may be timely addressed.Moreover, by utilizing the indoor fan of the climate control system todetermine duct leakage allows a user to determine leakage in the supplyduct and return ducts independently to thereby identify the location ofthe leak (assuming only one of either the supply duct or return duct isleaking). For instance, as will be discussed further herein, byactivating the indoor fan (positioned between the supply and returnducts) the indoor fan may isolate the supply duct from the return ductso that, for example, a leak within the return duct does not contributeto the leakage rate of the determined supply duct leakage rate.

Referring now to FIG. 1, a schematic diagram of a climate control system100 according to some embodiments is shown. In this embodiment, climatecontrol system 100 is a HVAC system, and thus, system 100 may bereferred to herein as HVAC system 100. In the illustrated embodiment,HVAC system 100 comprises a heat pump system that may be selectivelyoperated to implement one or more substantially closed thermodynamicrefrigeration cycles to provide a cooling functionality (hereinafter“cooling mode”), and/or a heating functionality (hereinafter “heatingmode”). In other embodiments, the HVAC system 100 is an air conditionerthat may only provide cooling through use of the refrigeration cycle.The HVAC system 100, configured as a heat pump system, may comprise anindoor unit 102, an outdoor unit 104, and a system controller 106 thatmay generally control operation of the indoor unit 102 and/or theoutdoor unit 104. In some embodiments, HVAC system 100 may insteadcomprise a packaged HVAC system that includes the function of the indoorunit 102 in a package located outdoors.

Indoor unit 102 generally includes an indoor heat exchanger 108, anindoor fan 110, an indoor metering device 112, and an indoor controller124. The indoor heat exchanger 108 may generally be configured topromote heat exchange between refrigerant carried within internal tubingof the indoor heat exchanger 108 and an airflow that may contact theindoor heat exchanger 108 but that is segregated from the refrigerant.Specifically, indoor heat exchanger 108 may include a coil 109 forchanneling the refrigerant therethrough that segregates the refrigerantfrom any air flowing through indoor heat exchanger 108 duringoperations. In some embodiments, the indoor heat exchanger 108 maycomprise a plate-fin heat exchanger. However, in other embodiments,indoor heat exchanger 108 may comprise a microchannel heat exchangerand/or any other suitable type of heat exchanger.

The indoor fan 110 may generally comprise a centrifugal blowercomprising a blower housing 111, a blower impeller 113 at leastpartially disposed within the blower housing 111, and a blower or indoorfan motor 115 configured to selectively rotate the blower impeller 113in a rotational first or nominal direction 117 about an axis of rotationof the blower impeller 113. As will be discussed further herein, indoorfan motor 115 may also be configured to rotate blower impeller 113 in arotational second or reverse direction 119 about the axis of rotation ofblower impeller 113 which is opposite the nominal direction 117. Indoorfan 110, comprising a centrifugal blower in this embodiment, isconfigured to provide or produce an airflow extending into an inlet ofindoor fan 110 in an inlet direction along the axis of rotation ofindoor fan 110, and out of an outlet of the indoor fan 110 in an outletdirection extending perpendicularly away from the axis of rotation ofindoor fan 110. Thus, irrespective of whether impeller 113 of indoor fan110 is rotated in either the nominal direction 117 or reverse direction119, indoor fan 110 produces an airflow extending along the inletdirection (extending along the axis of rotation of impeller 113) andoutlet direction (extending perpendicularly away from the axis ofrotation of impeller 113). The indoor fan 110 may generally beconfigured to provide airflow through the indoor unit 102 and/or theindoor heat exchanger 108 (specifically across or over the coil 109) topromote heat transfer between the airflow and a refrigerant flowingthrough the coil 109 of the indoor heat exchanger 108. The indoor fan110 may also be operated to rotate impeller 113 in the nominal direction117 as part of delivering temperature-conditioned air from the indoorunit 102 to one or more areas and/or zones of an indoor space. Forinstance, indoor fan 110 may rotate impeller 113 in the nominaldirection 117 as part of satisfying a request for cooling (when HVACsystem 100 is in the cooling mode) or a request for heating (when HVACsystem 100 is in the heating mode) as determined by system controller106 of HVAC system 100. The indoor fan 110 may generally be configuredas a modulating and/or variable speed fan capable of being operated atmany speeds over one or more ranges of speeds. In other embodiments, theindoor fan 110 may be configured as a multiple speed fan capable ofbeing operated at a plurality of operating speeds by selectivelyelectrically powering different ones of multiple electromagneticwindings of a motor of the indoor fan 110.

The indoor metering device 112 may generally comprise anelectronically-controlled motor-driven electronic expansion valve (EEV).In some embodiments, however, the indoor metering device 112 maycomprise a thermostatic expansion valve, a capillary tube assembly,and/or any other suitable metering device. In some embodiments, whilethe indoor metering device 112 may be configured to meter the volumeand/or flow rate of refrigerant through the indoor metering device 112,the indoor metering device 112 may also comprise and/or be associatedwith a refrigerant check valve and/or refrigerant bypass configurationwhen the direction of refrigerant flow through the indoor meteringdevice 112 is such that the indoor metering device 112 is not intendedto meter or otherwise substantially restrict flow of the refrigerantthrough the indoor metering device 112.

Outdoor unit 104 generally comprises an outdoor heat exchanger 114, acompressor 116, an outdoor fan 118, an outdoor metering device 120, areversing valve 122, and an outdoor controller 126. In some embodiments,the outdoor unit 104 may also comprise a plurality of temperaturesensors for measuring the temperature of the outdoor heat exchanger 114,the compressor 116, and/or the outdoor ambient temperature. The outdoorheat exchanger 114 may generally be configured to promote heat transferbetween a refrigerant carried within internal passages of the outdoorheat exchanger 114 and an airflow that contacts the outdoor heatexchanger 114 but that is segregated from the refrigerant. In someembodiments, outdoor heat exchanger 114 may comprise a plate-fin heatexchanger. However, in other embodiments, outdoor heat exchanger 114 maycomprise a spine-fin heat exchanger, a microchannel heat exchanger, orany other suitable type of heat exchanger. While not specifically shown,it should be appreciated that outdoor heat exchanger 114 may include acoil similar to coil 109 previously described above for indoor heatexchanger 108.

The compressor 116 may generally comprise a variable speed scroll-typecompressor that may generally be configured to selectively pumprefrigerant at a plurality of mass flow rates through the indoor unit102, the outdoor unit 104, and/or between the indoor unit 102 and theoutdoor unit 104. In some embodiments, the compressor 116 may comprise arotary type compressor configured to selectively pump refrigerant at aplurality of mass flow rates. In some embodiments, however, thecompressor 116 may comprise a modulating compressor that is capable ofoperation over a plurality of speed ranges, a reciprocating-typecompressor, a single speed compressor, and/or any other suitablerefrigerant compressor and/or refrigerant pump. In some embodiments, thecompressor 116 may be controlled by a compressor drive controller 144,also referred to as a compressor drive and/or a compressor drive system.

The outdoor fan 118 may generally comprise an axial fan comprising a fanblade assembly and fan motor configured to selectively rotate the fanblade assembly. The outdoor fan 118 may generally be configured toprovide airflow through the outdoor unit 104 and/or the outdoor heatexchanger 114 to promote heat transfer between the airflow and arefrigerant flowing through the outdoor heat exchanger 114. The outdoorfan 118 may generally be configured as a modulating and/or variablespeed fan capable of being operated at a plurality of speeds over aplurality of speed ranges. In other embodiments, the outdoor fan 118 maycomprise a mixed-flow fan, a centrifugal blower, and/or any othersuitable type of fan and/or blower, such as a multiple speed fan capableof being operated at a plurality of operating speeds by selectivelyelectrically powering different multiple electromagnetic windings of amotor of the outdoor fan 118. Further, in other embodiments, the outdoorfan 118 may comprise a mixed-flow fan, a centrifugal blower, and/or anyother suitable type of fan and/or blower.

The outdoor metering device 120 may generally comprise a thermostaticexpansion valve. In some embodiments, however, the outdoor meteringdevice 120 may comprise an electronically-controlled motor driven EEVsimilar to indoor metering device 112, a capillary tube assembly, and/orany other suitable metering device. In some embodiments, while theoutdoor metering device 120 may be configured to meter the volume and/orflow rate of refrigerant through the outdoor metering device 120, theoutdoor metering device 120 may also comprise and/or be associated witha refrigerant check valve and/or refrigerant bypass configuration whenthe direction of refrigerant flow through the outdoor metering device120 is such that the outdoor metering device 120 is not intended tometer or otherwise substantially restrict flow of the refrigerantthrough the outdoor metering device 120.

The reversing valve 122 may generally comprise a four-way reversingvalve. The reversing valve 122 may also comprise an electrical solenoid,relay, and/or other device configured to selectively move a component ofthe reversing valve 122 between operational positions to alter the flowpath of refrigerant through the reversing valve 122 and consequently theHVAC system 100. Additionally, the reversing valve 122 may also beselectively controlled by the system controller 106 and/or an outdoorcontroller 126.

The system controller 106 may generally be configured to communicatewith an indoor controller 124 of the indoor unit 102, an outdoorcontroller 126 of the outdoor unit 104, and/or other components of theHVAC system 100. In some embodiments, the system controller 106 may beconfigured to control operation of the indoor unit 102 and/or theoutdoor unit 104. In some embodiments, the system controller 106 may beconfigured to monitor and/or communicate, directly or indirectly, with aplurality of sensors associated with components of the indoor unit 102,the outdoor unit 104, etc. The sensors may measure or detect a varietyof parameters, such as, for example, pressure, temperature, and flowrate of the refrigerant as well as pressure and temperature of othercomponents or fluids of or associated with HVAC system 100. In someembodiments, the HVAC system 100 may include a sensor (or plurality ofsensors) for sensing or detecting the ambient outdoor temperature.Additionally, in some embodiments, the system controller 106 maycomprise a temperature sensor and/or may further be configured tocontrol heating and/or cooling of zones associated with the HVAC system100 (e.g., within the indoor space). In some embodiments, the systemcontroller 106 may be configured as a thermostat, having a temperaturesensor and a user interface, for controlling the supply of conditionedair to zones associated within the HVAC system 100.

The system controller 106 may be in communication with an input/output(I/O) unit 107 (e.g., a graphical user interface, a touchscreeninterface, or the like), which may be combined with or remote from thesystem controller 106, for displaying information and for receiving userinputs. The I/O unit 107 may display information related to theoperation of the HVAC system 100 (e.g., from system controller 106) andmay receive user inputs related to operation of the HVAC system 100.During operations, the I/O unit 107 may communicate received user inputsto the system controller 106, which may then execute control of HVACsystem 100 accordingly. Communication between the I/O unit 107 andsystem controller 106 may be wired, wireless, or a combination thereof.In some embodiments, the I/O unit 107 may further be operable to displayinformation and receive user inputs tangentially and/or unrelated tooperation of the HVAC system 100. In some embodiments, however, the I/Ounit 107 may not comprise a display and may derive all information frominputs from remote sensors and remote configuration tools (e.g., remotecomputers, servers, smartphones, tablets, etc.). In some embodiments,system controller 106 may receive user inputs from remote configurationtools, and may further communicate information relating to HVAC system100 to I/O unit 107. In these embodiments, system controller 106 may ormay not also receive user inputs via I/O unit 107.

In some embodiments, the system controller 106 may be configured forselective bidirectional communication over a communication bus 128. Insome embodiments, portions of the communication bus 128 may comprise athree-wire connection suitable for communicating messages between thesystem controller 106 and one or more of the HVAC system 100 componentsconfigured for interfacing with the communication bus 128. Stillfurther, the system controller 106 may be configured to selectivelycommunicate with HVAC system 100 components and/or any other device 130via a communication network 132. In some embodiments, the communicationnetwork 132 may comprise a telephone network, and the other device 130may comprise a telephone, smartphone, laptop, tablet computer, and otherportable computing/telecommunication devices. In some embodiments, thecommunication network 132 may comprise the Internet, and the otherdevice 130 may comprise a smartphone and/or other Internet-enabledmobile telecommunication device. In other embodiments, the communicationnetwork 132 may also comprise a remote server.

The indoor controller 124 may be carried by the indoor unit 102 and maygenerally be configured to receive information inputs, transmitinformation outputs, and/or otherwise communicate with the systemcontroller 106, the outdoor controller 126, and/or any other device 130via the communication bus 128 and/or any other suitable medium ofcommunication. In some embodiments, the indoor controller 124 may beconfigured to communicate with an indoor personality module 134 that maycomprise information related to the identification and/or operation ofthe indoor unit 102. In some embodiments, the indoor controller 124 maybe configured to receive information related to a speed of the indoorfan 110 when the impeller 113 of indoor fan 110 is rotated in either thenominal direction 117 or reverse direction 119, transmit a controloutput to an electric heat relay, control the rotational direction ofthe impeller 113 of indoor fan 110, transmit information regarding anindoor fan 110 volumetric flow-rate, communicate with and/or otherwiseaffect control over an air cleaner 136, and communicate with an indoorEEV controller 138. In some embodiments, the indoor controller 124and/or the system controller 106 may be configured to communicate withan indoor fan controller 142 in signal communication with the indoor fanmotor 115 of indoor fan 110 and/or otherwise affect control overoperation of indoor fan motor 115. For example, a sensor package 121(shown schematically in FIG. 1) in signal communication with indoor fancontroller 142 may measure speed and torque of indoor fan motor 115(when impeller 113 is rotated in either the reverse or nominalrotational directions 119, 117, respectively) and communicate themeasured speed and torque of indoor fan motor 115 to indoor controller124 and/or system controller 106. Sensor package 121 may include asensor for measuring rotational speed of an output shaft of indoor fanmotor 115 coupled to impeller 113, and a sensor for measuring torqueoutputted by the output shaft of fan motor 115; however, in otherembodiments, sensor package 121 may infer the speed and torque of indoorfan motor 115 through other measured parameters. In some embodiments,the indoor personality module 134 may comprise information related tothe identification and/or operation of the indoor unit 102 and/or aposition of the outdoor metering device 120.

The indoor EEV controller 138 may be configured to receive informationregarding temperatures and/or pressures of the refrigerant in the indoorunit 102. More specifically, the indoor EEV controller 138 may beconfigured to receive information regarding temperatures and pressuresof refrigerant entering, exiting, and/or within the indoor heatexchanger 108. Further, the indoor EEV controller 138 may be configuredto communicate with the indoor metering device 112 and/or otherwiseaffect control over the indoor metering device 112. The indoor EEVcontroller 138 may also be configured to communicate with the outdoormetering device 120 and/or otherwise affect control over the outdoormetering device 120.

The outdoor controller 126 may be carried by the outdoor unit 104 andmay be configured to receive information inputs, transmit informationoutputs, and/or otherwise communicate with the system controller 106,the indoor controller 124, and/or any other device 130 via thecommunication bus 128 and/or any other suitable medium of communication.In some embodiments, the outdoor controller 126 may be configured tocommunicate with an outdoor personality module 140 that may compriseinformation related to the identification and/or operation of theoutdoor unit 104. In some embodiments, the outdoor controller 126 may beconfigured to receive information related to an ambient temperatureassociated with the outdoor unit 104, information related to atemperature of the outdoor heat exchanger 114, and/or informationrelated to refrigerant temperatures and/or pressures of refrigerantentering, exiting, and/or within the outdoor heat exchanger 114 and/orthe compressor 116. In some embodiments, the outdoor controller 126 maybe configured to transmit information related to monitoring,communicating with, and/or otherwise affecting control over thecompressor 116, the outdoor fan 118, a solenoid of the reversing valve122, a relay associated with adjusting and/or monitoring a refrigerantcharge of the HVAC system 100, a position of the indoor metering device112, and/or a position of the outdoor metering device 120. The outdoorcontroller 126 may further be configured to communicate with and/orcontrol a compressor drive controller 144 that is configured toelectrically power and/or control the compressor 116.

System controller 106, indoor controller 124, outdoor controller 126,compressor drive controller 144, indoor fan controller 142, and indoorEEV controller 138 may each comprise any suitable device or assemblywhich is capable of receiving electrical (or other data) signals andtransmitting electrical (or other data) signals to other devices. Inparticular, while not specifically shown, controllers 106, 124, 126,138, 142, and 144 may each include a processor and a memory. Theprocessors (e.g., microprocessor, central processing unit, or collectionof such processor devices, etc.) may execute machine readableinstructions (e.g., non-transitory machine readable medium) provided onthe corresponding memory to provide the processor with all of thefunctionality described herein. The memory of each controller 106, 124,126, 138, 142, and 144 may comprise volatile storage (e.g., randomaccess memory), non-volatile storage (e.g., flash storage, read onlymemory, etc.), or combinations of both volatile and non-volatilestorage. Data consumed or produced by the machine readable instructionscan also be stored on the memory of controllers 106, 124, 126, 138, 142,and 144.

During operation, system controller 106 may generally control theoperation of HVAC system 100 through the indoor controller 124, outdoorcontroller 126, compressor drive controller 144, indoor fan controller142, and indoor EEV controller 138 (e.g., via communication bus 128). Inthe description below, specific control methods are described (e.g.,method 300). It should be understood that the features of thesedescribed methods may be performed (e.g., wholly or partially) by systemcontroller 106, and/or by one or more of controllers 124, 126, 138, 142,and 144 as directed by system controller 106. As a result, thecontroller or controllers of HVAC system 100 (e.g., controllers 106,124, 126, 138, 142, and 144, etc.) may include and executemachine-readable instructions (e.g., non-volatile machine readableinstructions) for performing the operations and methods described inmore detail below. In some embodiments, each of the controllers 106,124, 126, 138, 142, and 144 may be embodied in a singular control unit,or may be dispersed throughout the individual controllers 106, 124, 126,138, 142, and 144 as described above.

As shown in FIG. 1, the HVAC system 100 is configured for operating in aso-called cooling mode in which heat may generally be absorbed byrefrigerant at the indoor heat exchanger 108 and rejected from therefrigerant at the outdoor heat exchanger 114. Starting at thecompressor 116, the compressor 116 may be operated to compressrefrigerant and pump the relatively high temperature and high pressurecompressed refrigerant through the reversing valve 122 and to theoutdoor heat exchanger 114, where the refrigerant may transfer heat toan airflow that is passed through and/or into contact with the outdoorheat exchanger 114 by the outdoor fan 118. After exiting the outdoorheat exchanger 114, the refrigerant may flow through and/or bypass theoutdoor metering device 120, such that refrigerant flow is notsubstantially restricted by the outdoor metering device 120. Refrigerantgenerally exits the outdoor metering device 120 and flows to the indoormetering device 112, which may meter the flow of refrigerant through theindoor metering device 112, such that the refrigerant downstream of theindoor metering device 112 is at a lower pressure than the refrigerantupstream of the indoor metering device 112. From the indoor meteringdevice 112, the refrigerant may enter the indoor heat exchanger 108. Asthe refrigerant is passed through coil 109 of the indoor heat exchanger108, heat may be transferred to the refrigerant from an airflow that ispassed through and/or into contact with the indoor heat exchanger 108,the airflow being produced by the indoor fan 110 with the impeller 113of indoor fan 110 rotating in the nominal direction 117. Refrigerantleaving the indoor heat exchanger 108 may flow to the reversing valve122, where the reversing valve 122 may be selectively configured todivert the refrigerant back to the compressor 116, where therefrigeration cycle may begin again.

To operate the HVAC system 100 in the so-called heating mode, thereversing valve 122 may be controlled to alter the flow path of therefrigerant, the indoor metering device 112 may be disabled and/orbypassed, and the outdoor metering device 120 may be enabled. In theheating mode, refrigerant may flow from the compressor 116 to the indoorheat exchanger 108 through the reversing valve 122, the refrigerant maybe substantially unaffected by the indoor metering device 112, therefrigerant may experience a pressure differential across the outdoormetering device 120, the refrigerant may pass through the outdoor heatexchanger 114, and the refrigerant may re-enter the compressor 116 afterpassing through the reversing valve 122. Most generally, operation ofthe HVAC system 100 in the heating mode reverses the roles of the indoorheat exchanger 108 and the outdoor heat exchanger 114 as compared totheir operation in the cooling mode. Thus, in the heating mode, heat istransferred from the refrigerant to an airflow that is passed throughand/or into contact with the indoor heat exchanger 108, the airflowbeing produced by the indoor fan 110 with the impeller 113 of indoor fan110 rotating in the nominal direction 117.

Referring now to FIG. 2, a schematic diagram of an air circulation path200 of the HVAC system 100 of FIG. 1 is shown according to an embodimentof the disclosure. It will be appreciated that while three zones 202,204, 206 are shown, any number of zones, including a single zone, may bepresent in a structure or indoor space 201. Where present, the pluralityof zones may be conditioned independently or together in one or moregroups. The air circulation path 200 of the HVAC system 100 maygenerally comprise or be defined by a first zone supply duct 208, asecond zone supply duct 210, a third zone supply duct 212, a first zonereturn duct 214, a second zone return duct 216, a third zone return duct218, a main return duct 220, and a main supply duct 222. A plurality ofzone dampers 224 may be optionally provided. The air circulation path200 also passes through the indoor unit 102, which may include an indoorheat exchanger 108 and an indoor fan 110.

The air circulation path 200 of HVAC system 100 may also include aplurality of supply registers 226, 228 and 230, and a plurality ofreturn registers 232, 234, and 236. Supply registers 226, 228, and 230each define an interface between an end of one of the zone supply ducts208, 210, and 212 and one of the zones 202, 204, and 206 of the aircirculation path 200. For instance, a first supply register 226 definesthe interface between an end of the first zone supply duct 208 and thefirst zone 202 whereby air flowing through first zone supply duct 208passes through first supply register 226 before entering first zone 202.Similarly, return registers 232, 234, and 236 each define an interfacebetween an end of one of the zone return ducts 214, 216, and 218 and oneof the zones 202, 204, and 206 of the air circulation path 200. Forexample, a first return register 232 defines the interface between thefirst zone 202 and an end of the first zone return duct 214 whereby airwithin first zone 202 passes through first return register 232 prior toentering first zone return duct 214. Each register 226, 228, 230, 232,234, and 236 of HVAC system 100 may comprise a frame including a grilleand a damper positioned in the frame that is moveable between an openposition and a closed position configured to restrict or inhibit airflowtherethrough.

In operation, the indoor fan 110 may be configured to generate anairflow through the indoor unit 102 by rotating impeller 113 in thenominal direction 117 to deliver temperature conditioned air from an airsupply opening in the indoor unit 102, through the main supply duct 222,and to each of the plurality of zones 202, 204, 206 through each of thefirst zone supply duct 208, the second zone supply duct 210, and thethird zone supply duct 212, respectively. Additionally, each of thefirst zone supply duct 208, the second zone supply duct 210, and thethird zone supply duct 212 may optionally comprise a zone damper 224that regulates the airflow to each of the zones 202, 204, 206. In someembodiments, the zone dampers 224 may regulate the flow to each zone202, 204, 206 in response to a temperature or humidity sensed by atleast one temperature sensor and/or humidity sensor carried by at leastone of the system controller 106, a zone thermostat 158, and a zonesensor 160. In some embodiments, system controller 106 may be locatedexternal of indoor space 201, and indoor space 201 may not include zonethermostat 158 and/or zone sensor 160.

Air from each zone 202, 204, 206 may return to the main return duct 220through each of the first zone return duct 214, the second zone returnduct 216, and the third zone return duct 218. From the main return duct220, air may return to the indoor unit 102 through an air return openingin the indoor unit 102. Air entering the indoor unit 102 through the airreturn opening may then be conditioned for delivery to each of theplurality of zones 202, 204, 206 as described above. Circulation of theair in this manner may continue repetitively until the temperatureand/or humidity of the air within the zones 202, 204, 206 conforms to atarget temperature and/or humidity as required by at least one of thesystem controller 106, the zone thermostat 158, and/or the zone sensor160.

As described above, during operation a request may be communicated toindoor fan controller 142 (shown in FIG. 1) of indoor fan 110 fromsystem controller 106 (shown in FIG. 1) representative of, orcorresponding to, a desired airflow. Based on this requested airflowcommand and prior knowledge of the performance of indoor fan 110 in theindoor product application, the system controller 106 may estimate theairflow and the external static pressure (ESP) provided by indoor fan110 with impeller 113 rotating in the nominal direction 117 bycontinuously measuring motor speed and torque of the indoor fan motor115 of indoor fan 110 using sensor package 121. Particularly, componentsof indoor unit 102, including indoor heat exchanger 108 and indoor fan110 (including indoor fan motor 115), may be housed within a cabinet toform a self-contained air handling unit (AHU). Prior to installation ofindoor unit 102 at indoor space 201, the AHU of indoor unit 102 (oranother test AHU, including a test indoor fan, similar in configurationto the AHU of indoor unit 102) may be tested at an air plenum testfacility at a range of known airflows and ESPs (i.e., independentlymeasured by equipment of the test facility) to thereby create AHU mapscorrelating airflow and ESP of the AHU with motor speed and torque ofthe indoor fan 110 of the AHU. As a non-limiting example, a first AHUmap may include airflow along an X-axis thereof, motor power (which maybe calculated from a measured motor torque) along a Y-axis thereof, anda plurality of curves each corresponding to a fixed motor speed. In thismanner, an estimated airflow may be “looked-up” from the AHU map from aknown motor speed and torque. A second AHU map may include airflow alongan X-axis thereof, ESP along a Y-axis thereof, and a plurality of curveseach corresponding to a fixed motor speed, from which an estimated ESPmay be looked-up given the known motor speed and airflow (determinedfrom the first AHU map). However, additional functional relationshipsfor airflow and ESP may be used to correlate measured motor speed andtorque with estimated airflow and ESP.

The AHU maps created during testing may be stored in the memory of thesystem controller 106. In this manner, system controller 106 of HVACsystem 100 may apply measured motor speed and torque values communicatedto system controller 106 from indoor fan controller 142 to the AHU mapsstored in the memory of system controller 106 to thereby determine orlook-up an estimated airflow of the indoor fan 110 corresponding to themotor speed and torque of the indoor fan 110 measured by sensor package121. In some embodiments, the AHU maps may be stored in a memory ofindoor fan controller 142, and indoor fan controller 142 may apply motorspeed and torque values measured by sensor package 121 to the AHU mapsstored in the memory thereof to determine the estimated airflow ofindoor fan 110 corresponding to the measured motor speed and torque ofthe indoor fan 110. As will be discussed further herein, the memory of acontroller of HVAC system 100 (e.g., the memory of indoor controller 106and/or the memory of indoor fan controller 142) may include a forward ornominal AHU map or a set of first or nominal AHU maps corresponding toindoor fan 110 when the indoor fan 110 is operated such that impeller113 is rotated in the nominal direction 117. In other words, the nominalAHU maps corresponding to indoor fan 110 may be created by rotating theimpeller 113 of the indoor fan 110 of indoor unit 102 (or another testAHU, including a test indoor fan, similar in configuration to the AHU ofindoor unit 102) during the testing of the indoor unit 102 at the airplenum test facility in the nominal direction 117.

Referring now to FIGS. 1-3, a method 300 of determining duct leakage ina climate control system is shown in FIG. 3. In some embodiments, method300 may be practiced with HVAC system 100 as previously described above(see e.g., FIGS. 1, 2). Thus, in describing the features of method 300,continuing reference will made to the HVAC system 100 shown in FIGS. 1,2; however, it should be appreciated that embodiments of method 300 maybe practiced with other systems, assemblies, and devices.

Generally speaking, method 300 includes restricting airflow through atleast one duct (e.g., at least one of ducts 208, 210, 212, 214, 216,218, 220, and 222 of the air circulation path 200) of a climate controlsystem (e.g., the HVAC system 100). Method 300 may also generallyinclude operating an indoor fan (e.g., indoor fan 110) of the climatecontrol system to rotate an impeller (e.g., impeller 113) of the indoorfan in a reverse rotational direction (e.g., reverse direction 119)opposite a nominal rotation direction (e.g., nominal direction 117) ofthe impeller. Method 300 may further include determining or monitoringan airflow produced by the indoor fan when the impeller of the indoorfan is rotated in the reverse rotational direction, and determining aduct leakage rate associated with the at least one duct based on theairflow produced by the indoor fan. As will be described in more detailbelow, performance of some or all of the steps of method 300 may becyclical or repeated during the operational lifetime of the climatecontrol system so as to continually monitor a condition (e.g., leakagein one or more ducts) of the climate control system.

Initially, method 300 includes restricting airflow through at least oneduct of a climate control system at block 302. In some embodiments,block 302 may comprise a user of HVAC system 100 (e.g., a systeminstaller of HVAC system 100 and/or a technician qualified to serviceHVAC system 100) sealing-off the supply ducts 208, 210, 212, 222, and/orthe return ducts 214, 216, 218, 220 of the air circulation path 200 ofHVAC system 100. For example, if it is desired by the user of HVACsystem 100 to determine duct leakage in only the supply ducts 208, 210,212, 222 and not in return ducts 214, 216, 218, 220, then block 302 mayinclude sealing-off each of the supply ducts 208, 210, 212, and 222. Ifit is instead desired by the user of HVAC system 100 to determine ductleakage in return ducts 214, 216, 218, 220 then block 302 may includesealing-off each of the return ducts 214, 216, 218, and 220.

As will be described further herein, the user of HVAC system 100 mayindependently determine duct leakage in either the supply ducts 208,210, 212, 220 or the return ducts 214, 216, 218, 220 of air circulationpath 200 by selectively choosing to restrict airflow through supplyducts 208, 210, 212, 222 or return ducts 214, 216, 218, 220. In thismanner, if duct leakage is present, the user of HVAC system 100 maydetermine if the leak is in either one of the supply ducts 208, 210,212, 222 or in one of the return ducts 214, 216, 218, 220. In someembodiments, block 302 includes sealing-off at least one duct of HVACsystem 100 (e.g., ducts 208, 210, 212, 214, 216, 218, 220, and/or 222)by sealing a register (e.g., registers 226, 228, 230, 232, 234, and/or236) positioned at an end of the duct or ducts to be sealed. Forinstance, a user may seal-off zone supply ducts 208, 210, and 212 bysealing the supply registers 226, 228, and 230, respectively, via, forexample, sealably covering each of the grilles of supply registers 226,228, and 230 with adhesive tape, plastic wrap, a non-adhesive reusableseal and/or other means for quickly, conveniently, and cost-effectivelysealing supply registers 226, 228, and 230. Alternatively, block 302 maycomprise restricting airflow through at least one duct of the climatecontrol system by closing a zone damper associated with the at least oneduct. For example, block 302 may comprise restricting airflow throughmain supply duct 222 by closing each of the plurality of zone dampers224. In some embodiments, system controller 106 may close zone dampers224 either automatically via instructions stored in the memory of systemcontroller 106 for automatically periodically evaluating duct leakage inHVAC system 100, or in response entering a request into I/O unit 107.

Method 300 also includes operating an indoor fan of the climate controlsystem to rotate an impeller of the indoor fan in a reverse rotationaldirection opposite a nominal rotational direction of the impeller and toincrease a rotational speed of the impeller towards a maximum speed ofthe indoor fan at block 304. In some embodiments, block 304 may compriseoperating the indoor fan 110 of HVAC system 100 such that impeller 113is rotated in the reverse direction 119 and a rotational speed ofimpeller 113 in the reverse direction 119 is continuously increasedtowards a maximum speed of indoor fan 110. For example, block 304 mayinclude placing HVAC system 100 into an idle mode whereby indoor fan 110of HVAC system 100 remains idle and air is not circulated along the aircirculation path 200. The compressor 116 may also be inactive during theidle mode such that refrigerant is not actively being circulated throughthe heat exchanger 108.

Block 304 of method 300 may comprise transmitting a maximum reversespeed request from system controller 106 of HVAC system 100 to theindoor fan controller 142 such that a speed and an airflow produced byindoor fan 110 continuously increases from zero (corresponding to theidle mode of HVAC system 100) towards a maximum speed of the impeller113 that may be provided by the indoor fan 110 in the reverse direction119. In certain embodiments, system controller 106 of HVAC system 100may transmit the maximum reverse speed request to indoor fan controller142 in response to an input provided to system controller 106 (e.g., viaI/O unit 107 and/or device 130 of HVAC system 100) provided by a user ofHVAC system 100 (e.g., a system installer of HVAC system 100 or atechnician equipped to service HVAC system 100). Additionally, block 304may comprise placing HVAC system 100 into a fan-only mode as the speedof indoor fan 110 increased where compressor 116 of outdoor unit 104remains idle so that refrigerant is not circulated through indoor heatexchanger 108 as the speed of indoor fan 110 is increased.

As described above, indoor fan 110 produces airflow from an outletthereof when impeller 113 is rotated in the reverse direction 119, andthus reversing the direction of rotation of impeller 113 does notreverse the direction of airflow produced by indoor fan 110. However,given that impeller 113 of indoor fan 110 is configured to be operatedor rotated in the nominal direction 117 when HVAC system 100 is in thecooling and heating modes, operating indoor fan 110 to rotate impeller113 in the reverse direction 119 may alter one or more performancecharacteristics of indoor fan 110 relative to the performancecharacteristics of indoor fan 110 when operated to rotate impeller 113in the nominal direction 117. In other words, impeller 113 of indoor fan110 is configured such that the direction in which impeller 113 rotatesaffects the performance of indoor fan 110.

For example, rotating impeller 113 in the reverse direction 119 maydecrease a fan or blower efficiency of indoor fan 110 whereby the amountof airflow produced by indoor fan 110 (e.g., airflow in cubic feet perminute (CFM)) at a given input power (e.g., electrical input power inWatts (W)) provided to the indoor fan 110 is decreased. Thus, rotatingimpeller 113 in the reverse direction 119 may decrease the amount ofairflow produced by indoor fan 110 at a given rotational speed (e.g.,rotational speed in revolutions per minute (RPM)) of impeller 113.Further, given that ESP produced by indoor fan 110 is dependent upon theamount of airflow produced by indoor fan 110, rotating impeller 113 inthe reverse direction 119 may decrease the amount of ESP produced byindoor fan 110 (e.g., ESP in inches of water (in H₂O)) at a givenrotational speed of impeller 113.

Indoor fan 110 of HVAC system 100 may have an operational range ofrotational speeds ranging approximately between a minimum speed and amaximum speed, where operating indoor fan 110 at speeds less than theminimum speed and/or greater than the maximum speed may jeopardize thereliability of indoor fan 110 over its operational life as well asinterfere with the performance of indoor fan 110. For instance,operating indoor fan 110 at a speed less than the minimum operatingspeed may reduce the accuracy or resolution of the sensors of sensorpackage 121 configured to measure speed and torque of fan motor 115,thereby interfering with the determination or estimation of airflow andESP produced by indoor fan 110 that is based on the measurementsprovided by the sensors of fan motor 115 as described above.

In view of the above, it may be desirable to avoid operating indoor fan110 at a rotational speed outside of the operational range of indoor fan110. In some embodiments, the operational range of indoor fan 110 isapproximately between 200 RPM and 1,500 RPM; however, in otherembodiments, the operational range of indoor fan 110 may vary. In someembodiments, the average amount of airflow produced by indoor fan 110across the operational range of indoor fan 110 may be reduced byapproximately 85% when impeller 113 is rotated in the reverse direction119; however, the decrease in airflow resulting from rotating impeller113 in the reverse direction 119 rather than the nominal direction 117may vary. In certain embodiments, the average amount of ESP produced byindoor fan 110 across the operational range of indoor fan 110 may bereduced by approximately 80% when impeller 113 is rotated in the reversedirection 119; however, the decrease in ESP resulting from rotatingimpeller 113 in the reverse direction 119 rather than the nominaldirection 117 may vary. In some embodiments, indoor fan 110 may have anefficiency (e.g., air power produced by indoor fan 110 divided by inputpower supplied to indoor fan 110) of approximately 20% to 50% across itsoperational range when impeller 113 is rotated in the nominal direction117, and an efficiency of approximately 2% to 10% across its operationalrange when impeller 113 is rotated in the reverse direction 119;however, the efficiencies of indoor fan 110 when operated in the nominaland reverse directions 117, 119 may vary.

Method 300 proceeds by monitoring an airflow and an ESP produced by theindoor fan as the rotational speed of the indoor fan increases towardsthe maximum speed of the indoor fan at block 306. In some embodiments,block 306 comprises monitoring an airflow and an ESP produced by theindoor fan 110 of HVAC system 100 as the rotational speed of indoor fan110 increases towards the maximum speed of indoor fan 110. The airflowand ESP produced by indoor fan 110 may be monitored by a controller(e.g., system controller 106) of HVAC system 100. For example, theindoor fan controller 142 may transmit motor speed and torquemeasurements (provided by sensor package 121) of indoor fan motor 115 tosystem controller 106 where system controller 106 periodicallydeterminates or estimates airflow and ESP produced by the indoor fan 110based on AHU maps stored in the memory of system controller 106 and themotor speed and torque measurements transmitted from indoor fancontroller 142. Alternatively, indoor fan controller 142 and/or othercomponents of HVAC system 100 other than system controller 106 and insignal communication with indoor fan controller 142 may periodicallydetermine the airflow and ESP produced by the indoor fan 110 based onAHU maps stored in the memory of indoor fan controller 142 and/or theother components of HVAC system 100. In other embodiments, a flow sensorpositioned upstream and/or downstream of indoor fan 110 may be used tomeasure airflow produced by indoor fan 110.

In this embodiment, given that the performance and efficiency of indoorfan 110 is dependent upon the direction which impeller 113 is rotated,the AHU maps utilized by system controller 106 to estimate the airflowand ESP produced by indoor fan 110 as impeller 113 is rotated in thereverse direction 119 comprise a second or reverse AHU map or set ofsecond or reverse AHU maps corresponding to the indoor fan 110 when theindoor fan 110 is operated to rotate impeller 113 in the reversedirection 119. Thus, the memory of system controller 106 (or,alternatively, the memory of indoor fan controller 142) may include oneor more nominal AHU maps for estimating airflow and ESP produced byindoor fan 110 when impeller 113 is rotated in the nominal direction 117and one more reverse AHU maps for estimating airflow and ESP produced byindoor fan 110 when impeller 113 is rotated in the reverse direction119. The one or more reverse AHU maps corresponding to indoor fan 110may be created in a manner similar to the creation of the one or morenominal AHU maps described above. Particularly, prior to installation ofindoor unit 102 at indoor space 201, the AHU of indoor unit 102 (oranother test AHU, including a test indoor fan, similar in configurationto the AHU of indoor unit 102) may be tested at an air plenum testfacility with the impeller of the test indoor fan rotated in arotational reverse direction at a range of known airflows and ESPs tothereby create one or more reverse AHU maps correlating airflow and ESPof the AHU with motor speed and torque of the indoor fan 110 of the AHUwhen impeller 113 of indoor fan 110 is rotated in the reverse direction119.

Method 300 also includes determining whether the ESP of indoor fan 110(monitored at block 306) is equal to a first threshold ESP at block 308.In some embodiments, block 308 comprises determining whether a currentor most recently determined ESP of the indoor fan 110 of HVAC system 100is equal to a predetermined first threshold ESP. For example, as theairflow and ESP produced by indoor fan 110 is monitored by a controllerof HVAC system 100 (e.g., system controller 106), the controller mayperiodically compare the most recently determined ESP of indoor fan 110with the first threshold ESP to determine whether the ESP of indoor fan110 is equal to the first threshold ESP, where the first threshold ESPmay be pre-stored in the memory of the controller prior to theinstallation of HVAC system 100. In some embodiments, the firstthreshold ESP is approximately 0.1 in H₂O; however, in otherembodiments, the first threshold ESP may vary. For instance, in certainembodiments, the first threshold ESP may range approximately been 0.08in H₂O and 0.12 in H₂O.

The certainty and accuracy in which duct leakage may be detected maygenerally increase as ESP produced by the indoor fan 110 is increasedgiven that increasing ESP increases in-turn the amount of observableduct leakage within HVAC system 100 when a leak in present one of theducts (e.g., ducts 208, 210, 212, 214, 216, 218, 220, and/or 222) ofHVAC system 100. However, the amount of ESP that may be utilized fordetermining duct leakage in HVAC system 100 may be limited by thequality of seal employed to seal-off the duct to be evaluated forleakage at an end thereof. Specifically, sealing mechanisms which may bequickly and cost-effectively employed to seal, for example, supplyregisters 226, 228, and 230 to thereby seal-off zone supply ducts 208,210, and 212, such as plastic wrap, may be unable to maintain a seal ofsupply registers 226, 228, and 230 at ESPs substantially greater than0.1 in H₂O, necessitating the use of more expensive and cumbersome toinstall specialized sealing mechanisms if an ESP of substantiallygreater than 0.1 in H₂O is employed to evaluate duct leakage.

Further, the airflow provided by commonly utilized indoor fans ofclimate control systems at low ESPs (e.g., an ESP of 0.1 in H₂O) whenthe impeller of the indoor fan is rotated at a speed within theoperational range of the indoor fan may be too great for determiningduct leakage when the impeller is rotated in the nominal direction(e.g., nominal direction 117). In other words, the minimum speed of theindoor fan of a climate control system in at least some applications mayproduce an airflow or ESP of a magnitude (when the indoor fan isoperating in the nominal direction) which prevents the sealing of a ductof the climate control system to be evaluated using a convenientlyinstallable sealing mechanism (e.g., plastic wrap, etc.). Thus, in atleast some applications, a more expensive and cumbersome to installspecialized sealing mechanism may be required to seal-off the duct to beevaluated at an end thereof when the indoor fan of the climate controlsystem (being operated in the nominal direction) is utilized todetermine duct leakage.

However, by operating the indoor fan 110 in the reverse direction (e.g.,operating indoor fan 110 to rotate impeller 113 in the reverse direction119), the efficiency of the indoor fan may be degraded to an extentsufficient to permit the indoor fan to produce an ESP equal to the firstthreshold ESP while remaining within the operational range of the indoorfan. Particularly, impeller 113 of indoor fan 110 comprises a pluralityof impeller blades each having a geometry configured to maximize theefficiency of indoor fan 110 (e.g., airflow produced by indoor fan 110at a given input power) when impeller 113 is rotated in the nominaldirection 117. In other words, impeller 113 is specifically designed tobe rotated in the nominal direction 117 during operation of indoor fan110 in order to maximize the efficiency of indoor fan 110. Thus, theperformance of the blades of impeller 113 (e.g., the ability of theblades to create airflow at a given rotational speed of impeller 113)depends upon the direction in which impeller 113 is rotated, with theperformance of impeller 113 being degraded or reduced when impeller 113is rotated in the reverse direction 119 relative to the performance ofimpeller 113 when rotated in the nominal direction 117. Therefore, byoperating indoor fan 110 in the reverse direction 119, indoor fan 110may be utilized to determine or evaluate duct leakage in HVAC system 100while also employing a cost effective and convenient to install sealingmechanism (e.g., plastic wrap, etc.) to seal-off the duct (e.g., ducts208, 210, 212, 214, 216, 218, 220, and/or 222) of HVAC system 100 to beevaluated.

Moreover, by operating indoor fan 110 in the reverse direction 119 toproduce a low ESP equal to the first threshold ESP, duct leakage in HVACsystem 100 may be evaluated without needing to seal-off the ductsthereof. For example, duct leakage in main supply duct 222 of HVACsystem 100 may be evaluated by closing zone dampers 224 to restrictairflow through supply duct 222. Although some leakage across closedzone dampers 224 would occur with indoor fan 110 operated in the reversedirection 119, the amount of leakage across zone dampers 224 at the low,first threshold ESP would be minimal enough to permit evaluation of ductleakage within main supply duct 222. Particularly, prior to installationof indoor unit 102 at indoor space 201, zone dampers 224 may be testedat a test facility at a range of known airflows and ESPs (i.e.,independently measured by equipment of the test facility), including thefirst threshold ESP, to thereby map or characterize the expected airflowleaking across each zone damper 224 for the range of tested airflows andESPs when the zone damper 224 is closed. The mapped leakagecharacteristics of zone dampers 224 may be stored in the memory ofsystem controller 106 prior to installation of HVAC system 100.

If it is determined that the ESP of the indoor fan is equal to the firstthreshold ESP (i.e., the determination at block 308 is “Yes”), method300 may proceed by determining a duct leakage rate associated with theat least one duct at block 310. The duct leakage rate is based on theairflow of the indoor fan 110 at the first threshold ESP at block 310.The airflow of indoor fan 110 from which the duct leakage rate is basedon may be determined by system controller 106 based on the motor speedand torque measured by sensor package 121 of fan motor 115 and the oneor more reverse AHU motor maps stored in the memory of system controller106. In some embodiments, block 310 may also include returning ceasingrotation of the impeller 113 of indoor fan 110 in the reverse direction119 and returning HVAC system 100 to the idle mode.

In some embodiments, block 310 comprises determining a duct leakage rateassociated with either supply ducts 208, 210, 212, and 222, or returnducts 220, 232, 234, and 26 of HVAC system 100 based on the estimatedairflow of indoor fan 110 (e.g., airflow estimated by system control 106as described above) at the first threshold ESP. For example, whenairflow is restricted in each of supply ducts 208, 210, 212, and 222 atblock 302, the duct leakage rate determined at block 310 comprises thecollective duct leakage in supply ducts 208, 210, 212, and 222 of HVACsystem 100 at the first threshold ESP (the first threshold ESP in supplyducts 208, 210, 212, 222 comprising a positive ESP produced by indoorfan 110). Conversely, when airflow is restricted in each of return ducts214, 216, 218, and 220 at block 302, the duct leakage rate determined atblock 310 comprises the collective duct leakage in return ducts 214,216, 218, and 220 of HVAC system 100 at the first threshold ESP (thefirst threshold ESP in return ducts 214, 216, 218, and 220 comprising anegative ESP or vacuum produced by indoor fan 110).

Additionally, the duct leakage rate determined at block 310 may comprisethe estimated airflow of indoor fan 110 at the first threshold ESP whenairflow is restricted in the ducts (either each of the supply ducts oreach of the return ducts) of HVAC system 100 to be evaluated. Forexample, if airflow is restricted in supply ducts 208, 210, 212, and 222by sealing supply registers 226, 228, and 230, and an estimated airflowof approximately 124 CFM is provided by the indoor fan 110 (where indoorfan 110 is operated in the reverse direction 119) at a first thresholdESP comprising 0.1 in H₂O, then the duct leakage rate in supply ducts208, 210, 212, and 222 is determined to be approximately 124 CFM.Additionally, in embodiments where airflow is restrict through the atleast one duct (e.g., main supply duct 222) by closing the zone dampers(e.g., zone dampers 224) associated with the at least one duct ratherthan sealing-off an end of the at least one duct (via plastic wrap,etc.), the duct leakage rate determined at block 310 may comprisecorrecting the duct leakage rate based on the airflow of the indoor fan110 at the first threshold ESP (determined from motor speed and torquemeasured by sensor package 121 of fan motor 115 and the one or morereverse AHU motor maps) by the mapped leakage characteristics of theclosed ducts stored in the memory of system controller 106. For example,if airflow through main supply duct 222 is restricted by the closure ofzone dampers 224, and an estimated airflow of approximately 124 CFM isprovided by the indoor fan 110 at a first threshold ESP comprising 0.1in H₂O, and a leakage rate of approximately 5 CFM is estimated at an ESPof 0.1 in H₂O based on the mapped leakage characteristics of zonedampers 224, then the duct leakage rate would be determined to be 119CFM.

The duct leakage rate may also be expressed as a percentage of a nominalairflow rate of indoor fan 110. In some embodiments, the nominal airflowrate of indoor fan 110 may be the amount of airflow produced by indoorfan 110 when HVAC system 100 is operated in either the cooling orheating modes with the impeller 113 of indoor fan 110 being rotated inthe nominal direction 117. The nominal airflow rate may be pre-stored inthe memory of system controller 106 prior to the installation of HVACsystem 100. For instance, when HVAC system 100 is placed in either thecooling or heating modes to satisfy a demand for cooling or heating,system controller 106 may request indoor fan controller 142 to operateindoor fan 110 to produce the nominal airflow rate, whereby indoor fancontroller 142 provides an input power to the indoor fan motor 115sufficient to produce a motor speed and torque of indoor fan motor 115corresponding to the nominal airflow rate based on the one or morenominal AHU maps of indoor fan 110.

As an example of expressing the duct leakage, a memory of a controllerof HVAC system 100 (e.g., system controller 106) may include a nominalairflow rate of 1,500 CFM corresponding to the nominal airflow rate ofan indoor fan (e.g., indoor fan 110) of the climate control system andthus, the 124 CFM of airflow estimated by the controller when airflow isrestricted in supply ducts 208, 210, 212, and 222 provides a ductleakage rate associated with supply ducts 208, 210, 212, and 222 ofapproximately 8.3% of the nominal airflow rate at the first thresholdESP in this example. Thus, a controller of HVAC system 100 may determinea duct leakage rate associated with either the supply ducts 208, 210,212, and 222, or the return ducts 220, 232, 234, and 236 of HVAC system100 at the first threshold ESP in either CFM (with airflow beingrestricted through the at least one duct) or as a percentage of nominalairflow rate of the indoor fan 110 of HVAC system 100.

If it is determined that the most recently determined ESP of the indoorfan is not equal to the first threshold ESP (i.e., the determination atblock 308 is “No”), method 300 may proceed by determining whether therotational speed of the impeller of indoor fan is at the maximum speedof the indoor fan at block 312. In at least some embodiments, block 312comprises determining whether indoor fan 110 of HVAC system 100 is at amaximum speed thereof. For example, a controller of HVAC system 100(e.g., system controller 106) may determine, based on the motor speedand torque measured by sensor package 121, whether indoor fan 110 is atthe maximum speed thereof as defined by the operational range of indoorfan 110.

If it is determined that the rotational speed of the impeller is not atthe maximum speed of the indoor fan (i.e., the determination at block312 is “No”), method 300 may return again to block 304 and continue toincrease the rotational speed of the impeller towards the maximum speedof the indoor fan, the airflow and ESP produced by the indoor fan beingmonitored at block 306 as the rotational speed of the indoor fanincreased towards the maximum speed thereof. Thus, in some embodiments,blocks 308 and 312 may be performed periodically or cyclically as therotational speed of the fan continues towards the maximum thereof untilthe “Yes” determination is made at either block 308 or block 312. Forexample, as the rotational speed of the impeller 113 of indoor fan 110increases towards a maximum rotational speed of indoor fan 110, acontroller of HVAC system 100 (e.g., system controller 106) mayperiodically check or determine if either the ESP of indoor fan 110 isequal to the first threshold ESP (at block 308) or if the rotationalspeed of the impeller 113 has reached the maximum speed of indoor fan110 (at block 312).

If it is determined that the rotational speed of the impeller is at themaximum speed of the indoor fan (i.e., the determination at block 312 is“Yes”), method 300 may proceed by determining whether the ESP of theindoor fan is equal to or greater than a second threshold ESP at block314. In at least some embodiments, block 314 comprises determiningwhether a current or most recently determined ESP of the indoor fan 110of HVAC system 100 is equal to or greater than a predetermined secondthreshold ESP which is less than the first threshold ESP of block 308.For example, as the airflow and ESP produced by indoor fan 110 ismonitored by a controller of HVAC system 100 (e.g., system controller106), the controller may periodically compare the ESP of indoor fan 110with the second threshold ESP to determine whether the most recentlydetermined ESP of indoor fan 110 is equal to or greater than the secondthreshold ESP, where the second threshold ESP may be pre-stored in thememory of the controller prior to the installation of HVAC system 100.In some embodiments, the second threshold ESP is approximately 0.05 inH₂O; however, in other embodiments, the second threshold ESP may vary.For instance, in certain embodiments, the second threshold ESP may rangeapproximately been 0.02 in H₂O and 0.07 in H₂O. In certain embodiments,block 314 may also include ceasing rotation of the impeller 113 ofindoor fan 110 in the reverse direction 119 and returning HVAC system100 to the idle mode.

As described above, the accuracy in which duct leakage may be detectedgenerally decreases as the ESP of the indoor fan 110 at which the ductleakage determination is made decreases. Moreover, the more the secondthreshold ESP is reduced relative to the first threshold ESP, thegreater the extrapolation that is made from the second threshold ESP tothe first threshold ESP, reducing the accuracy of the duct leakagedetermination. Thus, the second threshold ESP, being lower than thefirst threshold ESP, may provide a lower bound where duct leakage maynot be accurately determined utilizing indoor fan 110 at an ESP that isless than the second threshold ESP. In applications where a relativelylarge leak is formed (e.g., a leak having a leakage rate equal to orgreater than 15%, for example) in either the supply ducts or returnducts to be evaluated, indoor fan 110 may only be able to produce an ESPthat is between the first and second threshold ESPs. As described below,method 300 provides a means for determining a duct leakage rate inapplications having a relatively large leak in the at least one duct tobe evaluated whereby the indoor fan (e.g., indoor fan 110) is preventedfrom achieving the first threshold ESP even when operating at themaximum speed of the indoor fan.

If it is determined that the most recently determined ESP of the indoorfan is equal to or greater than the second threshold ESP (i.e., thedetermination at block 314 is “Yes”), method 300 may proceed bydetermining a duct leakage rate associated with the at least one ductbased on a corrected airflow obtained by multiplying an estimatedairflow of the indoor fan by an airflow correction factor at block 316.In some embodiments, block 316 comprises determining a duct leakage rateassociated with either the supply ducts 208, 210, 212, and 222, or thereturn ducts 220, 232, 234, and 236 of HVAC system 100 based on acorrected airflow obtained by multiplying an estimated airflow of indoorfan 110 (estimated, e.g., from the motor speed and torque measured bysensor package 121 of fan motor 115 and the one or more reverse AHUmotor maps stored in the memory of system controller 106) by an airflowcorrection factor.

Generally, ESP produced by indoor fan 110 is positively correlated withairflow produced by indoor fan 110. Given the positive correlationbetween airflow and produced ESP, a corrected airflow at the firstthreshold ESP of indoor fan 110 may be determined or interpolated fromthe estimated airflow of indoor fan 110 at the currently or mostrecently determined ESP of the indoor fan using the airflow correctionfactor. For example, without being limited to this or any other theory,the airflow correction factor (Airflow_(correction)) may be obtained bythe following computation, where the first threshold ESP is representedby P nominal, the current or most recently determined ESP of the indoorfan is represented by P actual, and n represents a predeterminedconstant equal to 0.6 in this example:

$\begin{matrix}{{Airflow}_{correction} = \left( \frac{P_{nominal}}{P_{actual}} \right)^{n}} & (1)\end{matrix}$

The rate of duct leakage may be obtained by multiplying the estimatedairflow of the indoor fan 110 (estimated from the motor speed and torquemeasured by sensor package 121 of fan motor 115 and the one or morereverse AHU motor maps stored in the memory of system controller 106) atthe most recently determined ESP of the indoor fan by the correctionfactor Airflow_(correction), which may be determined in accordance withEquation (1) above. Thus, in the example provided above, P nominal, isequal to approximately 0.1 in H₂O, P_(actual), is equal to approximately0.07 in H₂O, and the correction factor Airflow_(correction) correctionis equal to approximately 1.24 according to Equation (1), therebyproviding a duct leakage rate of approximately 124 CFM at the firstthreshold ESP of 0.1 in H₂O. In this example, n of Equation (1)comprises a predetermined constant equal to 0.6 which may be pre-stored,along with Equation (1), in a controller of the climate control system(e.g., system controller 106 of HVAC system 100). Alternatively, n maybe determined by creating a curve-fit between a plurality of estimatedairflows from indoor fan 110 at a plurality of estimated ESPs rangingbetween the first and second threshold ESPs.

As with the duct leakage rate determined at block 310, the duct leakagerate in CFM determined at block 316 may also be expressed as apercentage of a nominal airflow rate of the indoor fan 110. Forinstance, with reference to the example described above, a controller ofHVAC system 100 (e.g., system controller 106) may estimate, based on oneor more reverse AHU maps stored in a memory thereof, that indoor fan 110produces 1,500 CFM at the first threshold ESP (0.1 in H₂O in thisexample) when airflow is permitted through supply ducts 208, 210, 212,and 222, and thus, the 124 CFM of corrected airflow estimated by thecontroller when airflow is restricted in supply ducts 208, 210, 212, and222 provides a duct leakage rate associated with supply ducts 208, 210,212, and 222 of approximately 8.3% at the first threshold ESP.

If it is determined that the most recently determined ESP of the indoorfan is not equal to or greater than the second threshold ESP (i.e., thedetermination at block 314 is “No”), method 300 may proceed bydetermining a duct leakage rate is greater than a predetermined maximumdeterminable duct leakage rate of the indoor fan at block 318. In otherwords, because the indoor fan 110 is unable to reach or exceed thesecond threshold ESP even though the rotational speed of the impeller ofthe indoor fan is at the maximum speed thereof, method 300 proceeds atblock 318 by determining that the duct leakage rate must be greater thanthe predetermined maximum determinable duct leakage rate of the indoorfan.

In at least some embodiments, block 318 comprises determining a ductleakage rate associated with at least one duct (e.g., ducts 208, 210,212, 214, 216, 218, 220, and/or 222) of HVAC system 100 is equal to orgreater than a predetermined maximum measurable duct leakage rate ofindoor fan 110 of HVAC system 100. In other words, block 318 may includedetermining that leakage in the at least one duct being evaluated is sogreat as to exceed the measurement capability of indoor fan 110 withimpeller 113 rotated in the reverse direction 119. The maximumdeterminable duct leakage rate may be determined from the one or morereverse AHU maps stored in the memory of a controller of HVAC system100. For example, the maximum determinable duct leakage rate may bebased on the maximum airflow producible by indoor fan 110 when rotated(in reverse direction 119) at the maximum speed thereof, wherein themaximum airflow estimated from the one or more reverse AHU maps storedin the memory of controller 106 In some embodiments, if the duct leakagerate exceeds the measurement capability of indoor fan 110 with impeller113 rotated in the reverse direction 119, method 300 may includeoperating indoor fan 110 in the nominal direction 117 to increase themaximum amount of airflow indoor fan 110 may produce within itsoperational range and thus the maximum measurable duct leakage rate ofindoor fan 110.

Following the determination of the duct leakage rate at either blocks310, 316, or 318, method 300 further includes issuing an alert to a userof the climate control system indicative of the duct leakage ratedetermined at blocks 310, 316, or 318 being greater, or equal to or lessthan a predetermined maximum permissible leakage rate at block 320. Insome embodiments, block 320 may indicate a negative result of theevaluation of the at least done duct of the climate control system byissuing an alert to a user of HVAC system 100 (e.g., a homeowner, aninstaller of HVAC system 100, and/or a technician qualified to serviceHVAC system 100) indicative of the leakage rate associated with eithersupply ducts 208, 210, 212, 222 or return ducts 214, 216, 218, 220 beingequal to or greater than maximum permissible leakage rate pre-stored inthe memory of a controller (e.g., system controller 106) of HVAC system100 prior to the installation of HVAC system 100. In certainembodiments, block 320 may indicate a positive result by issuing analert to the user of HVAC system 100 indicative of the leakage rateassociated with either supply ducts 208, 210, 212, 222 or return ducts214, 216, 218, 220 being equal to or less than the maximum permissibleleakage rate.

In some embodiments, the maximum permissible leakage rate comprises aleakage rate of approximately 6% of airflow produced by the indoor fan(e.g., indoor fan 110) at an ESP of 0.1 in H₂O of the indoor fan;however, in other embodiments, the maximum permissible leakage rate mayvary. For instance, the maximum leakage rate may comprise a leakage rateof approximately between 5% and 10% of airflow produced by the indoorfan at an ESP of 0.1 in H₂O of the indoor fan. The maximum permissibleleakage rate may be set at a value less than a leakage rate to beexpected in a newly and properly installed climate control system intypical applications. Thus, the maximum permissible leakage rate maycomprise a leakage rate obtainable in a properly installed andfunctioning climate control system in typical applications, with a ductleakage rate exceeding the maximum permissible leakage rate indicativeof an issue in either the installation of the climate control system ora physical defect or malfunction in one or more of the components of theclimate control system. For instance, a duct leakage rate (e.g., asdetermined at one of blocks 310, 316, or 318) in excess of the maximumpermissible leakage rate may indicate that the formation and/orenlargement of a leak path in at least one duct of the climate controlsystem which may inhibit or degrade the performance of the climatecontrol system.

Block 320 may comprise transmitting the alert to the user of HVAC system100 via I/O unit 107 and/or to the device 130 of HVAC system 100 viacommunication network 132 where the alert may be visually depicted tothe user of HVAC system 100. For example, device 130 may comprise aserver accessible by a system installer of HVAC system 100. In someembodiments, HVAC system 100 may be serviced by an installer of HVACsystem 100 and/or a technician qualified to service HVAC system 100 inresponse to receiving the alert issued at block 320. For example, theinstaller of technician may repair one or more ducts of HVAC system 100(e.g., one or more of ducts 208, 210, 212, 214, 216, 218, 220, and 222)to reduce the duct leakage rate of HVAC system 100. Method 300 may beexecuted to determine duct leakage in the climate control system uponinstallation of the climate control system and/or periodically duringthe operational life of the climate control system to ensure that theduct leakage rate of the climate control system remains less than themaximum permissible leakage rate defined by block 320 of method 300.

Still referring to FIGS. 1-3, through use of the systems and methodsdescribed herein (e.g., HVAC system 100, method 300, etc.), duct leakagein a climate control system may be accurately and timely determined ormonitored such that any issues or problems related to excessive ductleakage that may interfere with the performance of the climate controlsystem may be timely addressed. Specifically, a climate control systemfor an indoor space (e.g., HVAC system 100) may be operated to restrictairflow through least one duct (e.g., supply ducts 208, 210, 212, 222and return ducts 214, 216, 218, 220) of the climate control system(e.g., restricting airflow through at least one duct at block 302 ofmethod 300), operate an indoor fan (e.g., indoor fan 110) of the climatecontrol system to rotate an impeller (e.g., impeller 113 of indoor fan110) of the indoor fan in a reverse rotational direction (e.g., reversedirection 119) opposite a nominal rotational direction (e.g., nominaldirection 117) of the impeller whereby a fan efficiency of the indoorfan is reduced (e.g., operating the indoor fan at block 304 of method300), determine an airflow of the indoor fan when the impeller of theindoor fan is rotated in the reverse rotational direction (e.g.,monitoring an airflow of the indoor fan at block 306 of method 300), anddetermine a duct leakage rate associated with the at least one ductbased on the airflow of the indoor fan (e.g., determination made at oneof blocks 310, 316, and 318 of method 300).

Additionally, a controller (e.g., system controller 106 of HVAC system100) may comprise a non-transitory machine-readable medium includinginstructions that, when executed by a processor of the controller, causethe processor to operate an indoor fan of the climate control system torotate an impeller of the indoor fan in a reverse rotational directionopposite a nominal rotational direction of the impeller whereby a fanefficiency of the indoor fan is reduced, determine an airflow of theindoor fan when the impeller of the indoor fan is rotated in the reverserotational direction, and determine a duct leakage rate associated withthe at least one duct based on the airflow of the indoor fan whenairflow is restricted in the at least one duct.

By utilizing the indoor fan of the climate control system to determineduct leakage the necessity of utilizing specialized equipment providedby a third party vendor may be avoided. Additionally, duct leakage inone or more supply ducts of the climate control system may be evaluatedfor leakage independently of one or more return ducts of the climatecontrol system so that the location of a leak (if present) may beidentified as coming from either the supply ducts or return ducts of theclimate control system. Further, by rotating the impeller of the indoorfan in the reverse direction whereby the performance of efficiency ofthe indoor fan is degraded, sealing mechanisms (e.g., adhesive tape,plastic wrap, etc.) for quickly and cost-effectively sealing-off theducts of the climate control system may utilized in lieu of more costlyand potentially cumbersome to install specialized sealing mechanisms.

While exemplary embodiments have been shown and described, modificationsthereof can be made by one skilled in the art without departing from thescope or teachings herein. The embodiments described herein areexemplary only and are not limiting. Many variations and modificationsof the systems, apparatus, and processes described herein are possibleand are within the scope of the disclosure. Accordingly, the scope ofprotection is not limited to the embodiments described herein, but isonly limited by the claims that follow, the scope of which shall includeall equivalents of the subject matter of the claims. Unless expresslystated otherwise, the steps in a method claim may be performed in anyorder. The recitation of identifiers such as (a), (b), (c) or (1), (2),(3) before steps in a method claim are not intended to and do notspecify a particular order to the steps, but rather are used to simplifysubsequent reference to such steps.

What is claimed is:
 1. A method of operating a climate control systemfor an indoor space, the method comprising: (a) operating an indoor fanof the climate control system to rotate an impeller of the indoor fan ina reverse rotational direction opposite a nominal rotational directionof the impeller, wherein the indoor fan is configured to produce anairflow from an inlet to an outlet when the impeller is rotated in thenominal rotational direction and the direction of the airflow producedby the indoor fan does not reverse when the impeller of the indoor fanrotates in the reverse rotational direction; (b) determining the airflowof the indoor fan when the impeller of the indoor fan is rotated in thereverse rotational direction; (c) determining a duct leakage rateassociated with at least one duct of the climate control system based onthe airflow determined at (b), wherein airflow through the at least oneduct is restricted; and (d) determining an external static pressure(ESP) of the indoor fan when the impeller of the indoor fan is rotatedin the reverse rotational direction, wherein (c) further comprisesdetermining the duct leakage rate based on a corrected airflow of theindoor fan in response to a determination that the ESP determined at (d)is less than a predetermined first threshold ESP, wherein the correctedairflow comprises the airflow of the indoor fan determined at (b)multiplied by an airflow correction factor defined as:${AIRFLOWcorrection} = \left( \frac{Pnominal}{Pactual} \right)^{n}$where: AIRFLOWcorrection is the airflow correction factor; Pnominal isthe first threshold ESP; Pactual is the ESP of the indoor fan at (d);and n is a predetermined constant.
 2. The method of claim 1, wherein:the climate control system comprises a supply duct and a return duct,wherein the supply duct is sealed-off at an end thereof and airflow ispermitted through the return duct; and the duct leakage rate determinedat (c) comprises a duct leakage rate in the supply duct.
 3. The methodof claim 1, wherein: the climate control system comprises a return ductand a supply duct, wherein the return duct is sealed-off at an endthereof and airflow is permitted through the supply duct; and the ductleakage rate determined at (c) comprises a duct leakage rate in thereturn duct.
 4. The method of claim 1, wherein a register positioned atan end of the at least one duct is sealed.
 5. The method of claim 1,wherein (b) comprises determining the airflow of the indoor fan from ameasured speed and a measured torque of a fan motor of the indoor fan.6. The method of claim 1, wherein (c) further comprises determining theduct leakage rate in response to a determination that the ESP determinedat (d) is equal to a predetermined first threshold ESP.
 7. The method ofclaim 1, wherein the duct leakage rate determined at (c) comprises apercentage of a nominal airflow rate produced by the indoor fan when theclimate control system is activated in at least one of a cooling modeand a heating mode.
 8. A method of operating a climate control systemfor an indoor space, the method comprising: (a) operating an indoor fanof the climate control system to rotate an impeller of the indoor fan ina reverse rotational direction opposite a nominal rotational directionof the impeller, wherein the indoor fan is configured to produce anairflow from an inlet to an outlet when the impeller is rotated in thenominal rotational direction and the direction of the airflow producedby the indoor fan does not reverse when the impeller of the indoor fanrotates in the reverse rotational direction; (b) determining the airflowof the indoor fan when the impeller of the indoor fan is rotated in thereverse rotational direction; (c) determining a duct leakage rateassociated with at least one duct of the climate control system based onthe airflow determined at (b), wherein airflow through the at least oneduct is restricted; and (d) determining an external static pressure(ESP) of the indoor fan when the impeller of the indoor fan is rotatedin the reverse rotational direction, wherein (c) further includesdetermining the duct leakage rate exceeds a predetermined maximumdeterminable duct leakage rate of the indoor fan in response to adetermination that the ESP determined at (d) is less than a secondpredetermined threshold ESP, wherein the second threshold ESP is lessthan the first threshold ESP; wherein the first threshold ESP is between0.08 inches of H20 (in H20) and 0.12 in H20 and the second threshold ESPis between 0.02 in H20 and 0.07 in H20.
 9. The method of claim 1, themethod further comprising: (e) issuing an alert to a user of the climatecontrol system indicative of whether the duct leakage rate determined at(c) is greater than or less than a predetermined maximum permissibleleakage rate.
 10. The method of claim 1, wherein: the climate controlsystem comprises a supply duct and a return duct, and wherein a damperpositioned in the supply duct is disposed in a closed position torestrict airflow through the supply duct and airflow is permittedthrough the return duct; the duct leakage rate determined at (c)comprises a duct leakage rate in the supply duct.
 11. A climate controlsystem for an indoor space, the climate control system comprising: anindoor fan configured to produce an airflow through the indoor space; atleast one duct defining an air circulation path of the indoor space,wherein airflow through the at least one duct is restricted; acontroller to be coupled to the indoor fan, wherein the controller isconfigured to: operate the indoor fan to rotate an impeller of theindoor fan in a reverse rotational direction opposite a nominalrotational direction of the impeller, wherein the indoor fan isconfigured to produce an airflow from an inlet to an outlet when theimpeller is rotated in the nominal rotational direction and thedirection of the airflow produced by the indoor fan does not reversewhen the impeller of the indoor fan rotates in the reverse rotationaldirection; determine the airflow of the indoor fan when the impeller ofthe indoor fan is rotated in the reverse rotational direction; determinea duct leakage rate associated with the at least one duct based on theairflow of the indoor fan; and determine an external static pressure(ESP) of the indoor fan when the impeller of the indoor fan is rotatedin the reverse rotational direction, wherein determining the ductleakage rate includes determining the duct leakage rate based on acorrected airflow of the indoor fan in response to a determination thatthe ESP of the indoor fan is less than a predetermined first thresholdESP, wherein determining the duct leakage rate further includesdetermining the duct leakage rate exceeds a predetermined maximumdeterminable duct leakage rate of the indoor fan in response to adetermination that the ESP of the indoor fan is less than apredetermined second threshold ESP, wherein the second threshold ESP isless than the first threshold ESP.
 12. The climate control system ofclaim 11, wherein: the climate control system comprises a supply ductand a return duct, wherein the supply duct is sealed-off at an endthereof and airflow is permitted through the return duct; and thecontroller is configured to determine the duct leakage rate in thesupply duct based on the airflow of the indoor fan.
 13. The climatecontrol system of claim 11, wherein: the climate control systemcomprises a supply duct and a return duct, wherein the return duct issealed-off at an end thereof and airflow is permitted through the supplyduct; and the controller is configured to determine the duct leakagerate in the return duct based on the airflow of the indoor fan.
 14. Theclimate control system of claim 11, wherein the controller is configuredto: determine the duct leakage rate in response to a determination thatthe ESP of the indoor fan is equal to a predetermined first thresholdESP.
 15. The climate control system of claim 14, wherein the ductleakage rate comprises a percentage of a nominal airflow rate producedby the indoor fan when the climate control system is activated in atleast one of a cooling mode and a heating mode.
 16. The climate controlsystem of claim 11, wherein the controller is configured to issue analert to a user of the climate control system indicative of whether theduct leakage rate is greater than or less than a predetermined maximumpermissible leakage rate.